Support structures



Dec. 7, 1965 H. STRATTON ETAL SUPPORT STRUCTURES Original Filed April27, 1959 13 Sheets-Sheet 1 wvnvron HAL mwm'v xamr A Man win/v .1. mm

:r a: mum" BY Dec. 7, 1965 H. STRATTON ETAL SUPPORT STRUCTURES l3Sheets-Sheet :1

Original Filed April 27, 1959 Armani E") Dec. 7, 1955 H. STRATTON ETALSUPPORT STRUCTURES 13 Sheets-Sheet 3 Original Filed April 27, 1959 IIZ D7, 6 H. STRATTON ETAL SUPPORT STRUCTURES 13 Sheets-Sheet 4 OriginalFiled April 27, 1959 1965 H. STRATTON ETAL 3,221,506

SUPPORT STRUCTURES Original Filed April 27, 1959 1s Sheets-Sheet 5I.-I.llplnnawmnpl lpnppllapp4 INVENTORJ' JTTOf/VEDG? 1965 H. STRATTONETAL 6 SUPPORT STRUCTURES ori inal Filed April 27, 1959 13 eet eet 6 H41.rrmrro/v I .10 a; .9. mun r: awn MMA'M .x mm man a exam- IN VEN TORJDem 7, 1965 H. STRATTON ETAL 3,221,506

SUPPORT STRUCTURES Original Filed April 27, 1959 13 Sheets-Sheet 7 1965H. STRATTON ETAL 3,221,595

SUPPORT STRUCTURES Original Filed April 27, 1959 13 Sheets-Sheet 8...ul" llh......,l

{ H44 .rmarrm was" 5 Mr:

Ammo/v J mm 6) man a. Mam! QMMQ IMAM)? Dw. 1965 H. STRATTON ETAL3,221,505

SUPPORT STRUCTURES Original Filed April 27, 1959 13 Sheets-Shut 9 Q"Wlif/ 1965 H. STRATTON ETAL SUPPORT STRUCTURES Original Filed April 27,1959 13 Sheets-Sheet 11 1965 H. STRATTON ETAL 3,221,506

SUPPORT STRUCTURES Original Filed April 27, 1959 1:5 Sheets-Sheet 12INVENTORJ JTMRNE' a.

fill yumw I f I Dec; 1965 H. STRATTON ETAL I SUPPORT ST RUQTURESOriginal Filed April 27, 1959 13 Shani-511001. 15

llllllllllllllllllllllll I United States Patent 3,221,506 SUPPORTSTRUCTURES Hal Stratton, Los Angeles, Robert F. Bauer, Whittier, AlmeronJ. Field, Portuguese Bend, and Robert C. Crooke, Corona del Mar, Califl,assignors, by direct and mesne assignments, to Shell Oil Company, LosAngeles, Calif., a corporation of Delaware Continuation of applicationSer. No. 809,024, Apr. 27, 1959. This application Apr. 16, 1964, Ser.No. 360,807 11 Claims. (Cl. 61-46.5)

This invention relates to underwater platforms for supporting submergedequipment. This application is a continuation of our co-pendingapplication Serial No. 809,024, filed April 27, 1959, now abandoned.

The invention provides both method and apparatus for supportingunderwater equipment on completely submerged platforms located in bodiesof water which may vary in depth from relatively shallow to severalthousand feet. One important use of such platforms is the supporting ofelectronic and sonar gear used for the detection of submarines. For suchdetection equipment to be of maximum benefit, the supporting platformoften must be located many miles offshore, and consequently be supportedin water which may be thousands of feet deep, where pile driving isimpractical. Moreover, the platform must be accurately located andsecurely maintained at a depth of only a few hundred feet, so that invery deep water its supporting elements may have to be thousands of feetlong. This invention provides both method and apparatus for erectingsuch platforms in water of practically unlimited depth. a

In one form, the invention contemplates apparatus for supportingequipment uner a body of water overlying an earth formation whichincludes a buoyant platform completely submerged below the water surfaceand disposed on or above the formation. A downwardly extending leg isattached to the platform, and firmly anchored at its lower end to theformation. The platform has enough positive buoyancy to support anynormal load which may be applied to it, and avoid any tendency for theleg to buckle, even though the leg may be extremely long compared to itscross section.

In the preferred form of the invention, a plurality of downwardlyextending legs are used to hold the platform in place. The platform alsoincludes guide means extending toward the water surface so that anequipment support can be guided to and from the platform and disposed onit in an accurately known orientation.

In terms of method, the invention contemplates erecting apparatus forsupporting underwater equipment in a body of water overlying an earthformation. The method includes the steps of supporting a drilling rigover the formation, drilling a hole in the formation with the drillingrig, and disposing the lower end of an upwardly extending leg in thehole so that the lower end of the leg extends a substantial distancedown into the hole. The leg is'firmly anchored in the hole, say bycementing, or permitting the hole to collapse around the leg, and acompletely submerged platform with positive buoyance is secured to theleg.

In the preferred method, the platform includes a plurality of laterallyspaced holes. A separate hole is drilled from a floating vessel in theformation through each of the holes in the platform. A separate leg orcasing is 3,221,506 Patented Dec. 7, 1965 disposed in each of theplatform holes and secured at its upper portion to the platform and itslower end in a respective hole in the formation.

These and other aspects of the invention will be more fully understoodfrom the following detailed description in which:

FIG. I is a schematic elevation of the platform supported under afloating vessel from which an initial hole is being drilled into theformation through the center of the platform;

FIG. 2 is an enlarged plan view of the platform of FIG. 1;

FIG. 3 is a view, partly in section, taken on line 3-3 of FIG. 2;

FIG. 3A is an enlarged sectional view of a portion of the apparatusshown in FIG. 3 as directly under the platform.

FIG. 4 is a view taken on line 4-4 of FIG. 3;

FIG. 5 is a view of the platform lowered to its final position with afirst platform leg or casing being cemented in the formation;

FIG. 6 is a schematic elevation showing the completed installation ofthefirst leg and the beginning of the installation of a second leg forthe platform; 1

FIG. 7 is an enlarged sectional view, partially broken away, taken online 7--7 of FIG. 6;

FIG. 8 is an enlarged view of the area enclosed by line 88 of FIG. 6;

FIG. 9 is a schematic elevation of the platform with the second leg inplace and the hole for a third leg being drilled;

FIG. 10 is a perspective view of the platform completely installed withfive legs in place and with guide lines extending to the floatingvessel;

FIG. 11 is a schematic elevation of the initial step of locating abuoyant and submersible equipment support on the underwater platform;

FIG. 12 is a perspective view of the equipment support;

FIG. 13 is an elevation of the equipment support being lowered towardthe platform;

FIG. 14 is an elevation of the equipment support and a compressed airsupply means used in lowering the support to the platform;

FIG. 15 is an enlarged view, partly broken away, taken within the areaof line 1515 of FIG. 14;

FIG. 16 is a perspective view of the equipment support located on theplatform and left by the floating vessel; 1

FIG. 17 is a perspective view of an alternate platform using across-braced jacket for additional lateral stability; and

FIG. 18 is a sectional view of an alternate type of leg for anchoringthe platform.

Referring to FIG. 1, a compartmented platform 20 is suspended by guidecables 22 under a floating drilling barge 24 anchored by anchor lines 26in a body of water 28 over an earth formation 30 in which a hole 32 isbeing drilled from the floating vessel.

A drilling rig 34 mounted on the floating barge includes a derrick 36located over a collar or center well 38 opening out the bottom of thebarge. A drill pipe string includes a kelly joint 42 connected at itsupper end to a swivel 44 supported by a hook 46 attached to a travelingblock 48 which is in turn supported by a hoisting cable 50 disposed overa crown block 52 at the upper end of the derrick and connected to adrawing works 54 on the deck of the floating barge. The kelly jointextends down through a rotary table 56 which is revolved in a horizontalplane by a rotary table power unit 58 mounted on the derrick floor.

The lower end of the kelly joint 42 is connected to a downwardlyextending length of drill pipe string 60 made up of individual sectionsof drill pipe coupled together in conventional fashion and extendingdown into the hole. A drill collar 64 and underreamer bit 65 on thelower end of the drill pipe string are used to form the hole to. adiameter slightly larger than the outside diameter of a downwardlyextending casing or pipe 66 disposed coaxially around the drill string.The casing is supported at its upper end by a pair of easing lines 67,or by other conventional means such as a casing spider (not shown). Eachcasing line is releasably attached at one end to the casing and at theother end to a respective winch (not shown) in the floating barge.

Sea water is circulated from a pump 68 through a hose 70 connected tothe swivel. The sea water flows down the kelly and out the lower end ofthe drill string 60 so that cuttings formed by the rotating bit andunderreamer are washed back up out of the hole 32 and onto the oceanfloor.

Tobegin the operation shown in FIG. 1, the buoyant compartmentedplatform 20 is towed into close proximity of the floating barge, whichis moored with the anchor lines over the desired location for theplatform. The anchor lines permit the vessel to pitch and roll due towave action, and to move in a limited orbit due to wind and current. Theguide lines 22 are extended from constant tension winches (not shown,but located under the derrick in the floating barge) down through thecenter well of the barge and attached to guide cones 72 connected to theupper side of the buoyant platform. As shown most clearly in FIG. 2,there are five sets of guide cones with three cones in each set disposedequiangular around five separate sleeves 74 and seats 76 permanentlyfixed to the platform 20 and extending vertically through the platformin a S-spot pattern.

As shown in FIGS. 2 and 3, the platform includes a rectangular flat top77, a pair of end walls 78, a pair of side walls 79, a bottom 80, a pairof central tanks 81, a pair of intermediate tanks 82, and a pair ofouter tanks 84. The tanks are separated by downwardly extending verticalpartitions 85 welded along their edges to the underside of the platformtop, and at their ends to the side walls of the platform.

The platform 20 is towed adjacent the floating barge, and submerged andkept level by selectively flooding the compartments until it has aslight negative buoyancy, the weight of the submerged platform beingtaken on the guide lines 22 connected to the winches on the floatingbarge. Air is most conveniently released from a compartment by placingone end of a U-shaped tube 83 in the trapped air space of a compartmentthrough the vent hole 16 in the platform bottom 80 and keeping the otherend of the tube at a suitable elevation (say at the water surface) topermit air to be displaced. Once negative buoyancy of platform 20 hasbeen obtained by bleeding air from compartments 81, 82 and'84 throughtube 83, the tube is withdrawn from the compartment. The U- shaped tube83 is operated and positioned from the barge 24. The vertical positionof the open end of the reversely bent portion of the tube 83 determinesthe level to which water will rise in the compartment in which the tubeis engaged.

Using a guide system which is described below, or using a diver standingon the platform, which is located at a relatively shallow depth belowthe floating barge, say about feet, the lower end of a length of a firstcasing 66 is stabbed from the barge through the center guide sleeve 74in the platform. Alternatively, the casing can be guided through theSleeve by manipulation from the barge, if the platform is raisedsufliciently close to the bottom of the barge to permit visualobservation. The initial casing may be of any suitable size, say 16" indiameter, and preferably making a close sliding fit in the sleeve.Additional sections of 16" casing are screwed onto the upper end of thecasing to form'the first casing string or leg, and the casing string isrun to within a few feet'of the ocean floor, and hung or suspended bythe casing lines 67 from the floating barge. The drill string, drillcollars and underreamer bit are made up, run through the casing, anddrilling of the desired amount of hole 32 is commenced using ocean wateras a circulating fluid to wash drill cuttings out of the hole 32 backonto the ocean floor.

After sufl'icient hole has been drilled to receive the .required amountof easing, say 800-1000 feet, the upper end of drill pipe 60 isdisconnected from the kelly joint at the floating barge, and a swage 86,say 16" x 18", on the lower end of a joint 88 of a secondary or 18"casing is stripped down over the drill pipe and screwed onto the upperend of the 16" casing 66 which is suspended below well 38 by cable 67.The drill string 60 temporarily is left standing in hole 32. The stringof 16" casing then is lowered from the vessel through platform 20 towardthe hole and the swage 68 is lowered toward platform 29, using the drillpipe 60 as a guide. The drill pipe 60 is withdrawn from the hole afteradditional 18" casing is added to permit the casing string 88 to belowered to a point adjacent the top 77 of platform 20 where a J-slotsetting tool 90 on the exterior of the swage 86 can be engaged with fouroutwardly extending lugs 92 welded 90 apart on an upwardly extendingcylindrical mandrel 94 welded at its lower end around the central sleeveof the platform. When the setting tool 90 is engaged with mandrel 94,the lower end of the 16" casing 66 is disposed in the mouth of the hole32. The platform is later lowered with respect to the barge according toa procedure to be described below; in lowering the platform the casing66 is introduced into hole 32.

Referring to FIG. 4, the setting tool 90 includes a cylindrical skirt 96with an annular top 98 welded to the skirt and swage. Four invertedJ-slots open out of the lower edge of the skirt 90 apart.

The casing string 66 and 88 is lowered, until the lower edge of theskirt 90 rests on the lugs. The casing string 66, 88 is then slowlyrotated in a counterclockwise-direction (as viewed from above) until theopen end of each slot is over a respective lug. The skirt and easingstring then drops a short distance, and further rotation of the casingbrings the closed end of each slot against a respective lug. The casingis then lifted to lock the skirt and mandrel together as shown in FIG.4. In this manher, the weight of the platform is transferred from theguide line supports 22 to the casing string 88, which is suspended atits upper end by elevators (not shown) hung from the derrick.

While the platform is still suspended a relatively shallow distancebelow the floating barge with the casing 88 locked thereto, a diver islowered to connect the casing string 66 to the central, intermediate,and outer tanks 81, 82 and 84 of the platform with a pair of first airhoses 100, a pair of second air hoses 102, and a pair of third air hoses104, respectively. The lower and inner end of each of the first airhoses has a nipple 106, which is screwed into a threaded opening 107 inthe 16" casing string 66 just below the platform. The lower and innerends of the second pair of hoses each have a respective nipple 108screwed into each of a pair of second threaded openings 109 below thefirst opening in the casing, and the lower and inner ends of the thirdpair of air hoses each have a respective nipple 110 screwed into each ofa pair of third threaded openings 111 in the casing below the secondpair. The outer and upper end of each air hose is conncctcd to itsrespective compartment by a nipple 112 screwed into a respectivethreaded hole 114 in the platform bottom underlying each compartment.Each nipple 112 includes a check valve which permits air to flow onlytoward the adjacent compartment. Each compartment also includes arespective venting hole 116 in the tank bottom so that each compartmentis, in effect, open-bottomed. (It is through the vent holes 116 that theU-shaped tube 83 is engaged when the platform is initially flooded intoa condition of negative buoyancy.) The casing 66 also includes a pair ofpurging ports 118 located below the pair of third openings 111. Asmentioned above, the reversely bent portion of the U-shaped tube 83 isintroduced into the-compartment through vent holes 116 in order toinitially place the platform 20 in a negatively buoyant condition.

The entire assembly of casing 66, 88 and platform 20 is lowered intoplace by making up additional joints of 18" casing 88 on the floatingbarge. During lowering of platform 20, casing 66 is stabbed into hole32. Lowering is done after air lines 100, 102 and 104 have beenconnected to casing 66. If the block load on the derrick becomesexcessive due to the additional sections of casing 88 added to thecasing string, the lowering process is temporarily halted, and air ispumped down the casing to force pressurized air out the air lines 100,102 and 104 to displace water from the platform compartments through thevents 116 and thereby reduce the load on the derrick block. If desired,a swab cup 120 may be connected on the lower end of a string of drillpipe 60 which is reinserted into casing 88 as shown in FIG. 3A tocontrol the point of entry of air into the platform compartments tostabilize the platform, the drill pipe 60 having been withdrawn fro-mcasing 66 and 88 after the process of adding lengths of .casing 88 toengage swage 86 with mandrel 94. As shown in FIG. 3A, a swab cup 120 ispositioned to permit compressed air, pumped down through casing 66 and88, to enter air lines and 102. Escape of compressed air from thecompartments is prevented by the presence of the check valves andnipples 112.

After the platform 20 has been lowered to the desired depth below thesurface of the water to position the lower end of casing 66 in hole 32,the swab cup is run in on the lower end of the drill pipe to a positionabove purging ports 118 in the 16" casing but below the third set of airports. The first leg or string of casing is then cemented by pumpingcement 122 (shown in FIG. 5) through the length of drill string 60mounting swab cup 120, out the lower end of the casing 66 and up theannular space between the casing 66 and the hole 32. After the casing 66has been cemented in place sufiicient to maintain its final position,say as shown in FIG. 5, with its lower end resting in the bottom of thehole 32, the casing 88 is set in slips (not shown) at the main decklevel, the drill string 60 and swab cups are removed from casing 88, andsufiicient air is pumped into the platform 20 so that it has sufficientbuoyancy to hold the casing string in an erect and upright position.

A casing packer or plug 124 (FIG. 7), which may be of conventional oilfield design, is set approximately 200 feet below the water surface inthe 18" casing just below a backolf joint 126 in the second string ofcasing 88. The backotf joint is made up of left-handed threads while theremaining joints of the casing string 88 are righthand threads. Thecasing packer has a vertical conduit 128 through itwith a check valve130 in it to permit air to be pumped down through the packer but preventair from flowing up the other direction. Using a suitable packingarrangement (not shown) at the upper end of the casing 88, water isdisplaced out the purging ports 118 by pumping compresed air down theupper end of the 18" casing until the casing has adequate buoyancy tomaintain itself in an upright position. The 18" casing above theb'ackoff joint 126 is then removed.

Approximately 250 feet of 24" diameter casing 132 15 stripped down overthe 18" casing. The upper end of the 24" casing is closed with a cap134, which is secured to a hoisting line 136. The remainder of the 24"casing is then lowered down over the 18" casing until it comes to restas shown in FIG. 7. The upper end of the hoisting line is secured to amarking buoy 138, which floats on the water surface for easy locationand retrieving of the 24" casing. The guide lines 22 are kept slack andthe first leg is held upright by its own buoyancy and by the buoyancy ofthe platform while the cement sets independent of any movement of thefloating barge.

As shown in FIG. 7, the backoff joint includes an upwardly and outwardlyextending tapered section at its lower end 138, which matches a similarsection on the upper end of an inwardly extending annular lip 142 on thelower end of the 24" casing. To facilitate the stripping of the 24"casing down the 18" casing, as described above, the lower end of the 24"casing is disposed around the 18" casing before the backoff joint ismade up in the 18" casing. Thereafter, the backotf joint is added, andadditional sections of 18" and 24 casing are added as the platform islowered to the positions shown in FIGS. 5 and 6.

As shown in FIG. 6, after setting the first platform leg, the barge isthen moved approximately 25 feet to the right to be directly above asecond casing seat 143 and sleeve 144 in the platform (see FIG. 8). Ifthe platform, now in its lower and permanent position, is at a depth toogreat for divers, the second leg or string of 16" casing 145 is run inwith a guide assembly 146 as shown in FIG. 8. The assembly includes aguide sleeve 148 with three radially extending horizontal arms 149 (onlytwo of the arms are visible in FIG. 8) attached to it. The outer end ofeach arm is connected to an upright pipe 150. A separate hollow cone152. each open at its upper and lower end, is welded to the lower end ofa respective pipe, and a separate guide line is disposed through eachone of the pipes. The lower end of a second leg or string of casing isplaced in the casing guide sleeve 148 on the drilling barge, and thenthe guide assembly and lower end of the casing are lowered as shown inFIG. 8. The three cones on the guide assembly 146 seat on the threematch ing cones around the second sleeve 143 on the platform, and centerthe guide assembly sleeve and lower end of the casing directly over thesecond seat and sleeve. The 16 casing 145 is then lowered through theplatform until it is within a few feet of the ocean bottom. Then thecasing guide assembly is pulled back to'the surface by a wire line 154attached to the sleeve 148. The identical drilling tools describedpreviously, including a drill string 60. are then run through the secondcasing, and a second hole 155 (see FIG. 9) is drilled and underrea'medas previously described, a joint of casing 145 being added to the secondcasing string for the initial stabbing of the second casing string inthe second hole 155. The drill pipe is then withdrawn. A second stringof 18 casing 157 is made up and lowered to a point where a swage 156 islanded in the second casing seat 143 on the sleeve 144 of the platform.Swab cups on a drill pipe: are lowered in the second 16" casing 145,which extends to the floating vessel, to a point past the swage, and thesecond string of 16" casing 145 is cemented as previously described. Ifdesired, concentric strings of casing as required can be set to minimizemaximum fiber stress in the'legs. Upon the completion of the setting ofthese concentric strings, the excesscasing above the platform is backedoff at the deck of the platform (see FIG. 10) by the means of a backoffjoint (not shown) located just above the swage. The vessel is then movedto start a hole for the third leg or third string of casing 160 as shownin FIG. 9. Connection between the buoyant platform 20 and the secondcemented casing 145 is maintained between the swage 156 and slot 143.

The foregoing is repeated for the third, fourth, and fifth strings ofcasing 160, 161, 162, respectively, so that the final platforminstallation with five legs is as shown in FIG. 10.

The platform is now ready to receive an equipment array support 164 asshown in FIGS. ll, l2, l3, I4, 15 and. 16. The specific equipment (notshown) carried by the support is not a part of this invention, andtherefore is not described.

The equipment array s pport includes a rectangular horizontal flat base166, a separate vertical side tank 168 mounted on the top of the base ateach of the sides of the base, and a vertical center tank 170 disposedbetween the two side tanks so that in plan view the tanks are in theconfiguration of an H. Each of the side tanks includes a lower valve 172in its lower portion and an upper valve 174 at its upper portion. Aseparate combination air hose and hoisting cable 176 is connected toeach upper valve' on each side tank. A vertical sleeve 178 extends downthrough the central portion of the center tank and the base. The upperend of the sleeve projects a short distance above the top of the centertank to serve as a mandrel 180. A pair of outwardly extending lugs 182are welded to the lower portion of the mandrel at diametrically opposedlocations. The lower portion of the sleeve has perforations 184 openinginto the central tank, which also includes opening 186 in its lowerleft-hand corner as viewed in FIG. 12 so that the center tank is ineffect an open-bottom tank.

The bottom of the base includes fifteen vertical openings 188 throughit, the lower end of each of the openings being disposed andflaredoutwardly to have a conical 'form to mate-with a repective cone 72 onthe platform.

The equipment support is towed by a tug 190 to within close proximity ofthe floating barge as shown in FIG. 11, the tanks on the support basebeing full of air so that the equipment support has positive buoyancy.

The guide lines 22 are each strung through a respective opening in thesupport base as shown in FIG. 11, and then led back to a respectiveconstant tension winch (not shown) on the floating barge. The separaterespective 'air hoses and hoisting cables are run from the underside ofthe floating barge to the upper valves 174 on each of theside tanksofthe equipment support. ment'suppolt is then submerged and swung toposition aproximately 100 feet under the barge by selective flooding ofthe buoyant chambers. This is accomplished by opening upper valves 174in the air hoses and opening lower valves 172 in the bottom of the sidetanks. The side tanks are completely filled with water, and the airtrapped in the center tank is compressed to a reduced volume so thesupport has a negative buoyancy. The support sinks and swings directlyunder the floating barge, where it is held by the combination air linesand cables.

The marker buoy 138 is removed from the line 136, which is then passedup through the sleeve 178 in the equipment support, and'the 24" casingis then pulled up through the sleeve in the equipment support. A slidingjoint assembly 200 (see FIG. 14) is stripped down over the 24" casing132. The sliding joint assembly (shown in detail in FIG. 15) includes alower blow-out preventer 202 on its lower end, an intermediate blow-outpreventer 204 connected by a conduit 206 to the upper end of the lowerblow-out preventer, a lower tube 208 connected at its lower end to theintermediate blow-out preventer, and slidably disposed in an upper tube210 to form a slip joint, and an upper blow-out preventer 212 on theupper end of the upper tube. The mating ends of the lower and uppertubes have annular internal stops 213 to prevent them from coming apartwhen the slip joint is placed in tension. An ring 214 in an annulargroove 215 in the stop in the lower end of the upper tube makes a highpressure sliding seal against the lower tube. The upper blow-outpreventer is supported by a pair of slip joint cables 216. The lowerblow-out preventer is actuated through a first control line 217 to sealon the mandrel 180 above the top center tank on the equipment support.The lower end of the lower blow-out preventer has invertcd J-slots 217Aopening out its lower edge to tit on The equipthe mandrel lugs 182 andmechanically lock the slip joint assembly to the equipment support, asdecribed for the system shown in FIG. 4. The intermediate and upperblow-out prcventers are actuated through control lines 218. 219.respectively, to seal against the 24" casing. An air supply line 220 isconnected to the conduit between the intermediate and lower blow-outpreventers.

The equipment array support is lowered in successive steps by the use ofthe derrick traveling blocks to handle the slip joint assemblysuspension cables 216 and the combination air and support cables 176 forthe support. Before each increment of lowering, the sliding joint iscollapsed by releasing the upper blow-out preventer from its sealagainst the 24" casing 132. Then the upper blowout preventer is sealedon the 24 casing by charging preventer 212 with compressed air throughline 219 with the slip joint collapsed. The intermediate blow-outpreventcr 204 is then released from engagement with the 24" casing 132by releasing the compressed air charge of the preventer, and as thesupport cables on the equipment array support are payed out, the slipjoint extends because of the negative buoyancy of the support 164.During the increment of lowering, the air volume of the support is heldconstant by continually pumping air into the center of the tank 170 tocompensate for the loss of air volume due to the increasing hydrostatichead and due to water which enters tank 170 as the slip joint 200 isoperated. As shown best in FIG. 15, the air is supplied to the centertank as the support is lowered by supplying air under increasingpressure through the air hose 220. The air flows down the annular spacebetween the 24 casing and the sleeve 178 in the support. The air thenpasses out the ports 184 opening into the bottom of the central tank.The Water displaced from the central tank flows out through the-opening186 in the bottom corner of the tank. When the slip joint is fullyextended, the

- intermediate blow-out preventer is sealed against the 24 casing byair-charging preventer 204 via line 218, and the slip joint againcollapsed. by releasing the air-charge in upper preventer 212, asexplained above. By this means, the array support is safely controlledand landed on the tension casing platform as shown in FIG. 16. Eachconical recess in the bottom of the equipment support mates with acorresponding cone on the platform to guide the Support into anaccurately reproducible position.

When the equipment array support is landed in the position shown in FIG.16, the blow-out preventers are then released and the slide jointassembly is pulled to the surface after lower blow-out preventer 202 isreleased from lugs 182. The air in the center tank does not escape whenthe blow-out preventers are disconnected because the ports leading fromthe central tank sleeve into the central tank are located at the bottomof the tank below the water level in the tank. For situations wherechange of negative buoyancy due to air dissolving in the water maypresent a problem, another light fluid is used instead of air in thetanks of both the platform and the equipment array support. Oil, or agas such as methane, which has a lower solubility in water, may be used.Another precautionary measure to insure maintenance of the propernegative buoyancy is the periodic pumping of fresh fluid into the tanksof the platform and equipment support. The platform tanks 81, 82, 84 areproportioned so that with all the platform tanks full of air, the upwardbuoyant force of the platform is insufficient to rupture the platformlegs or to pull them from the formation. The equipment support tanks aresized so that with the side tanks flooded and the central tank full ofair, the support has a negative buoyancy. The negative buoyancy of theequipment support 164 is less than the constant positive buoyancy ofplatform 20.

The line on the 24 casing is connected to a submerged buoy 240. and thecasing is lowered to the position shown in l'lG. to. The guide lines andthe combination air and lifting lines on the side tanks of the equipmentsup ort are also secured to buoy 240 which is about 50 feet or so belowthe water surface to be clear of seagoing traffic and yet be easilyreached by a diver when necessary.

The equipment support is raised from the platform by any of severalalternative procedures using any suitable barge (not shown), which hasadequate mooring gear, air compressors, and lifting capacity for theload on the platform. Using a diver, the lifting cables for the supportand the guide lines connected to the platform are picked up off of thesubmerged buoy and secured to respective winches on the floating vessel.The array support is then lifted to a point approximately 100 feet belowthe surface. During this lifting operation, the cable load remainsconstant, because the air in the center tank expands and escapes out thebottom of the tank as the support is raised. The air hoses on the bargeare connected to the air hoses leading to the side tanks, which are thenpartly dewatered by the application of compressed air from the barge.The servicing barge is pulled off to one side, and the side tanksfurther dewatered so the equipment support floats to the surface.

If necessary, prior to the lifting operation, the 24" guide casing israised and the blow-out preventers on the slipjoint assembly are loweredto add make-up air to the center tank to decrease the load to be raised.This is done by lifting cable 136 from buoy 240, raising the 24" casing132 to the surface, and then engaging a slip joint assembly 200 over thecasing 132 as described above.

If there is some concern about the condition of the lifting cables, newcables are attached to the upper blowout preventer on the guideassembly, and the slide assembly is then lowered over the 24" guidecasing and latched onto the outwardly extending lugs on the mandrel atthe top of the array support. The array is then lifted by the newcables.

In case cables are inadequate, the array is lifted by stripping a newstring of casing (not shown) over the 24" guide casing. The lower jointof the new casing has a J-slot similar to that shown in FIG. 4, whichengages the outwardly extending lugs 230 on the mandrel on the top ofthe array. The entire equipment array support is then hoisted by the newcasing.

FIG. 17 shows an alternate embodiment of the invention in which acrossbracedjacket 250 is attached to the underside of the platform toincrease the rigidity of the legs to which the platform is attached. Thejacket includcs a separate downwardly extending sleeve 252 welded to theunderside of the platform around each one of the four holes spacedaround the center hole of the platform. Each jacket sleeve makes a closesliding fit around the respective casing extending through it.Preferably, the lower ends of each jacket sleeve are welded to its retspective casing leg. The four jacket sleeves 252 are rigidly attached toeach other by cross-bracing members 254. The cross-braced jacket isattached to the underside of the platform either on the floating vesselor on shore before the platform is carried to the underwater location.The drilling of each hole for the platform legs takes place through eachof the jacket sleeves with the platform suspended underneath thefloating vessel as previously described. The welding, if done, of eachjacket sleeve to its respective leg is done while the platform is stillsuspended a relatively shallow depth below the floating vessel and canreadily be reached by divers. The advantage of the platform with thecross-braced jacket is that the platform has increased rigidity andresistance to lateral and torsional displacement due to underwatercurrent action.

An alternate arrangement for increasing the life of the legs holding theplatform is shown in FIG. 18, in which a chain 260 is coaxially disposedin the lower portion of a casing leg 262 and attached at its lower endto an anchor spider-264 disposed across the lower end of the casing leg.The upper end of the chain is attached to a vertical bolt 266 disposedin a bore 268 extending through a plug 270 having a taper on its lowerend to match the internal taper of the swage 272 in the casing leg andseated in an opening 274 of the platform 276. The chain and anchor blockare set in the lower portion of the casing as it is initially loweredinto the hole, as previously described, and when the swage is made upinto the casing leg. the plug 270 is added and a nut 278 on the upperend of the bolt is tightened to put the chain in tension, and to relievesome of the initial tension on the casing. The plug includes a pluralityof vertical ports 280 through it to permit cement to be pumped down thecasing (this arrangement is used for the four corner legs, which do nothave air ports and purging ports as previously described for the centerleg). After the swage is made up into the casing leg and additionalcasing sections are added above the swage, the casing is lowered to aseat 282 on the platform. A slug of cement 284 is then pumped down thecasing, and followed by a column of oil 286 to displace the cement tothe position shown in FIG. 18. The ports in the plug have check valves288 to prevent upward flow and yet permit downward flow of fluid such ascement and oil. With this arrangement, the lower portion of the chain iscemented in the casing, and the upper portion of the chain is surroundedby the oil in the casing. Thus, the chain is protected against corrosionfor an indefinite period, thereby greatly extending the life of the leg,because even after the leg is finally weakened by corrosion, the chainwill still have its original strength. The same is true for concentricstrings of easing cemented together as previously described.

Although the foregoing description is specific to the platform beingspaced above the ocean floor, it will be apparent that the platform canalso be disposed on the ocean floor if desired.

With the apparatus of this invention, electronic or sonic equipment onthe support is accurately moved to and from a fixed position usingmethods and apparatus which are relatively simple and inexpensive, evenin water depths of thousands of feet.

We claim:

1. A subsurface structure comprising in combination equipment ofpredetermined vertical height and weight for carrying out a desiredfunction underwater, a platform, means within the platform to storefluid to give the platform a positive buoyancy in excess of its ownweight and that of the equipment, means for landing and holding theequipment on the platform, and at least one vertical tubular columnfastened at its upper end to the platform and anchored at its lower endin the bottom of the'water body, the tubular column between the bottomand the platform being substantially shorter in length than thedifference between the water depth and the combined vertical height ofthe equipment and the platform so that the equipment supported on theplatform is at its upper extremity substantially below the surface ofthe water body, the tubular column being under tension in response tothe positive buoyancy of the platform. a

2. Apparatus according to claim 1 including guide and seat meansconnected to the platform and extending upwardly therefrom, an equipmentsupport member including internal buoyancy regulating chambers and meansfor engaging the guide and seat means, the equipment support memberhaving negative buoyancy of an absolute value less than the positivebuoyancy of the platform when the support member engaging means areengaged with the platform guide and seat means, air conduit meansconnected to the buoyancy regulating chambers and extending upwardtherefrom to terminate at a location below the surface of the body ofwater, and check valve means in the air conduit means, the buoyancy ofthe equipment support member being alterable from a condition ofnegative buoyancy to a condition of positive buoyancy to raise thesupport member from the platform.

3. Apparatus according to claim 1 which includes a plurality of tanks inthe platform, a plurality of vertically spaced conduit means connectingthe leg below the platform to the tanks, and vertically reciprocablemeans in the leg selectively operable relative to the conduit means froma location above the water surface to admit compressed air from a sourceof compressed air disposed at location above the water surface toselected ones of the conduit means for regulation of the contents of thetanks.

4. A subsurface structure comprising in combination equipment ofpredetermined vertical height and weight for carrying out a desiredfunction underwater, a platform, means within the platform to storefluid to give the platform a positive buoyancy in excess of its ownweight and that of the equipment, at least one vertical tubular columnfastened at its upper'cnd to the platform and anchored at its lower endin the bottom of the water body, the tubular column between the bottomand the platform being substantially shorter in length than thedifference between the water depth and the combined vertical height ofthe equipment and the platform so that the equipment supported on theplatform is at its upper extremity substantially below the surface ofthe water body, the tubular column being under tension in response tothe positive buoyancy of the platform, and a plurailty of guide cablesextending from the platform toward the water surface for guiding theequipment to the platform from the surface.

5. A subsurface structure comprising in combination equipment ofpredetermined vertical height and weight for carrying out a desiredfunction underwater, a platform, means within the platform to storefluid to give the platform a positive buoyancy in excess of its ownweight and that of the equipment, and means for landing and holding theequipment on the platform, a plurality of vertical tubular columnsfastened at their upper ends to the platform and anchored at their lowerends in the bottom of the water body, the tubular columns between thebottom and the platform each being substantially shorter in length thanthe difference between the water depth and the combined vertical heightof the equipment and the platform so that the equipment supported on theplatform is at its upper extremity substantially below the surface ofthe water body, the several columns each being under tension in responseto the positive buoyancy of the platform.

6. Apparatus for supporting equipment below the surface of a body ofwater overlying an earth formation, the formation constituting the lowerlimit of the body of water, the apparatus comprising a hollow platformof substantially constant positive buoyancy completely submerged beneaththe water surface and spaced above the formation, a hollow tensionallystressed leg having an elongate extent between spaced apart oppositeends substantially less than the depth of the body of water attached tothe platform at one end thereof to extend downwardly into a hole in theformation, means for firmly sealing the other end of the leg in thehole, an elongated leg stress reducing member disposed in the leg andanchored at its lower end within the hole against upward movement andconnected at its upper end to the upper end of the leg, andmeansconnected between the leg and the upper end of the member forattaching the upper end of the member to the leg and for restraining thebuoyant platform from upward movement relative to the leg in the eventof leg failure.

7. Apparatus for locating and supporting equipment under a body of wateroverlying an earth formation, the apparatus comprising a unitary buoyantplatform having contiguous buoyant portions submerged beneath the watersurface and spaced above the formation, substantially entirely verticalmeans for spacing the platform from the formation comprising adownwardly extending leg having an elongate extent less than thevertical distance between the water surface and the formation, means forattaching the upper end of the leg to the platform in conjunction with aplatform buoyant portion, means for firmly anchoring the lower end ofthe leg to the formation, a completely submerged negatively buoyantequipment bearing support member disposed on the platform, and means formoving the equipment support member up and down with respect to theplatform, the leg constituting the sole connection between the formationand the platform.

8. Apparatus according to claim 7 including means for changing thenegative buoyancy of the equipment support member during operation ofthe means for moving the equipment support member up and down withrespect to the platform.

9. Apparatus according to claim 7 wherein the equipment support memberis hollow and has its interior open to the exterior of the equipmentsupport member at a lower portion thereof, and including means connectedto a source of gas disposed above the water surface and to the supportmember for adding gas to the interior of the equipment support memberfor regulating the buoyancy of the equipment support member.

the platform, a plurality of tubular sleeves extending verticallythrough the platform at preselected locations on the platform, eachsleeve being sealed in fixed watertight relation to the upper and lowersurfaces of the platform, a plurality of vertical hollow legs extendingbetween the platform and the earth formation, each leg having anelongate extent between its upper and lower ends less than the verticaldistance between the water surface and the earth formation, each leghaving its upper extent disposed. in a corresponding sleeve, meansconnecting each leg to its corresponding sleeve adjacent the uppersurface of the platform to secure the platform from upward movementrelative to the leg, means securing the lower end 'of each leg withinthe earth formation, one of the legs extending above the platform towardthe water surface, an initially positively buoyant hollow equipmentbearing support defining a plurality of watertight tanks internallythereof, each of the support tanks being open at a lower portion thereofto the extension of the support, means for flooding at least one of thesupport tanks to render the support negatively buoyant, a verticalsleeve extending through the support, the said one leg extending throughthe sleeve, means selectively operable from a location above the watersurface to move the support up and down with respect to the platform,and means engageable between the platform and the support for locatingthe support in a predetermined position on the platform, the supporthaving a negative buoyancy when positioned on the platform of an amountless than the positive buoyancy of the platform. I

11. Apparatus according to claim 10 including selectively operable meansremovably connectible to the support and engageable with the said oneleg for lowering the support to the platform by movement along the saidone leg, the support being negatively buoyant during operation of theselectively operable means, and means connected to the at least onesupport tank and to a source of gas located above the water surface foradmitting gas to the tank to regulate the buoyancy of the support duringoperation of the selectively operable means.

References Cited by the Examiner UNITED STATES PATENTS 2,187,871 1/1940Voorhees -8 2,476,309 7/1949 Lang 175-8 2,503,516 4/1950 Shrewsburg61-465 X 2,512,783 6/1950 Tucker 175-6 2,555,145 5/1951 McKinney.

2,606,003 8/1952 McNeil] 175-7 2,691,272 10/1954 Townsend et al. 61-465X (Other references on following page) UNITED STATES PATENTS OTHERREFERENCES Willis er 61-465 X The on Weekly (publication), February1947, pp. Ka mo 61-69 3335. McNelll 1757 Cox et a] 166 46 5 The 011& GasJournal (pubhcatlon), October 1957, pp. Parks 6l--46.5 X 100-101. Baueret a1. 175-7 Bauer et a1 175-7 EARL J. WITMER, Primary Examiner. B6153.62 X I m JACOB SHAPIRO, Examiner.

1. A SUBSURFACE STRUCTURE COMPRISING IN COMBINATION EQUIPMENT OFPREDETERMINED VERTICAL HEIGHT AND WEIGHT FOR CARRYING OUT A DESIREDFUNCTION UNDERWATER, A PLATFORM, MEANS WITHIN THE PLATFORM TO STOREFLUID TO GIVE THE PLATFORM A POSITIVE BUOYANCY IN EXCESS OF ITS OWNWEIGHT AND THAT OF THE EQUIPMENT, MEANS FOR LANDING AND HOLDING THEEQUIPMENT ON THE PLATFORM, AND AT LEAST ONE VERTICAL TUBULAR COLUMNFASTENED AT ITS UPPER END TO THE PLATFORM AND ANCHORED AT ITS LOWER ENDIN THE BOTTOM OF THE WATER BODY, THE TUBULAR COLUMN BETWEEN THE BOTTOMAND THE PLATFORM BEING SUBSTANTIALLY SHORTER IN LENGTH THAN THEDIFFERENCE BETWEEN THE WATER DEPTH AND THE COMBINED VERTICAL HEIGHT OFTHE EQUIPMENT AND THE PLATFORM SO THAT THE EQUIPMENT SUPPORTED ON THEPLATFORM IS AT ITS UPPER EXTREMITY SUBSTANTIALLY BELOW THE SURFACE OFTHE WATER BODY, THE TUBULAR COLUMN BEING UNDER TENSION IN RESPONSE TOTHE POSITIVE BUOYANCY OF THE PLATFORM.